Streptococcus pneumoniae

Drug-resistant Streptococcus pneumoniae


Nutrition— The metabolic processes of S. pneumoniae are similar to a large number other bacteria, in the fact that it uses fermentation as its sole mechanism for metabolizing carbohydrates (Carbohydrate Utilization, 2001).  An online book by Dr. Kenneth Todar of the University of Wisconsin—Madison states that S. pneumoniae is an anaerobic bacteria that is aerotolorint (Todar, 2012). This means that its ATP is produced by the fermentation of simple sugars within the cell, much like you would find in organisms that live in oxygen poor or inept environment. Though S. pneumoniae has an anaerobic means of producing ATP, it is not limited to only anaerobic environments. For example,  Dr. Todar states that only 20% of fresh clinical isolates for S. pneumoniae required a fully anaerobic, zero oxygen, environment in order to ferment properly (Todar, 2012). This ability to thrive in oxygen rich and poor environments allows S. pneumoniae to metabolism sugars almost anywhere giving it a massive competitive edge over many other bacteria. This is an ability that is common amongst many pneumonia causing bacteria and distinguishes S. pneumoniae form other bacterial groups.
Figure 1: Diagram of the fermentation process of glucose in an anaerobic environment. Tanner Folvag 2013.


The Importance of Enzymes-- As we have stated before on our CLASSIFICATIONS page, S. pneumoniae is a member of a group known as the lactic acid bacteria (LAB). LAB bacteria have a variety of distinguishing features that are semi-unique to these bacteria. One of the most important distinguishing features is their genetic inability to encode for the enzyme catalase (Hoskins, et. al., 2001). This inability to produce catalase (an enzyme used to break down H2O2) largely determines the nutritional habits of the S. pneumoniae bacteria because, as an anaerobe, it produces large quantities of hydrogen peroxide as a by product of its metabolism (Pericone, 2000). This inability to produce catalase naturally has raised many questions amongst bacteriologist as to why bacteria, such as S. pneumoniae, that produce hydrogen peroxide in such toxic amounts can not diffuse the problem on their own (Pericon, 2000). This is why S. pneumoniae must obtain the enzyme from its surrounding environment. To metabolize sugars correctly and efficiently S. pneumoniae bacteria prefers to live in places like the upper respiratory systems due to the high abundance of catalase produced by either the host or other bacteria living there as well (Gruner, et. al., 2007).



Figure 2: Digital representation of the enzyme catalase. Jawahar Swaminathan, 2009. 


 What do S. Pneumonia like to eat?-- S. pneumonia requires a variety of mono- and polysaccharides as well as carbohydrates in order to obtain the carbon and energy it needs to continue growth (Lyer, 2005). Even though S. pneumonia is capable of utilizing a variety of sugars, not all sugars are created equal. This is to say that S. pneumonia make decisions to use one source of energy over another to optimize its energy yield (Lyer, 2005). The mechanism that regulates these selections is known as carbon catabolite repression (CR) (Paulson, 1996). This mechanism is very complex in S. pneumonia but primarily relies upon one key enzyme known as catabolite control protein A (CcpA) to govern the metabolic decisions of the bacteria.  In a basic sense the CcpA enzyme has an affinity toward cretin types of simple and complex sugars. Once a highly preferred sugar is detected, the enzyme will shut off genes that code for proteins and other transport mechanisms designed for less preferred sugars (Rosenow, 1999). This shut down of non-essential genes allows for a much more efficient metabolism of more useful sugars, thus yielding more energy (Lyer, 2005). A study conducted in 2005 by Dr. Carsten concluded that S. pneumonia’s most preferred simple sugar is in fact sucrose (Rosenow, 1999).

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